Silicon esters



United States Patent Ofifice 4 3,029,269 Patented Apr. 10, 19623,029,269 SELIQON ESTERS Andrew D. Abbott, Ross, and Robert 4). Bolt,San Rafael, Caiifi, assignors to Jalifornia Research Corporation, SanFrancisco, alif., a corporation of Delaware No Drawing. lFiied Aug. 21,1956, er. No. 605,422 6 Claims. (Cl. 260-448.8)

This invention relates to the preparation of novel silicon estercompounds. These compounds have excellent viscosity andtemperature-viscosity characteristics and are well adapted foremployment as hydraulic fluids and for other lubricant purposes.

The compounds of this invention are of the type having the generalformula:

r i l R -()-SlOR2-OSIIOR l R1 R3 where the R s and the R s are saturatedaliphatic radicals of from 1 to 16 carbon atoms each and R is a divalenthydrocarbon radical of from 2 to 18 carbon atoms, at least two of whichare in a chain between the adjacent oxygen atoms, which is free ofaliphatic unsaturation.

Certain preferred compounds of this invention within the abovedescription are those of the types having the general formula I I 0 O RR where the R s and the R s are saturated aliphatic radicals of from 1to 16 carbon atoms each and R is a divalent hydrocarbon radical of from3 to 18 carbon atoms, at least three of which are in a chain between theadjacent oxygen atoms, which is free of aliphatic unsaturation. Thevarious R s may represent the same or different radicals, and the sameis true with respect to the R radicals. Representative R and R radicalsare methyl, ethyl, isopropyl, sec.-butyl, terL-butyl, amyl, isoamyl,tert.amyl, cyclopentyl, cyclohexyl, 2-ethylbutyl, Z-ethylhexyl, decyl,dodecyl, and the like, while representative R radicals are1,3-propylene, 1,3- and 1,4-butylene, 1,3-, 1,5- and 2,4-pentylene, 1,4-and 2,6-hexylene, 1,8-octylene, 1,10-decylene, 1,3- and1,4-cyclohexylene, 1,3- and 1,4-phenylene, and 3,5-tolylene.

and 3,5 -tolylene.

The silicate esters of the above type according to this invention have alow pour point and good viscosity and viscosity index properties,coupled with low volatility even at high temperatures. Thus, the presentcompounds are adapted to be used at temperatures even below 65 F., whiletheir viscosity at 210 F. is unusually good, i.e., from about 1.5 to cs.The ASTM slope of the viscosity-temperature curves of the presentcompounds is from about 0.61 to 0.70 as measured from 100 to 210 F.,while relatively low slope values are indicative of correspondingly highviscosity-index qualities.

In view of the foregoing properties, and since the present compounds ofthe above type are somewhat combustion resistant, it is obvious thatsaid compounds are well adapted to be used as synthetic lubricants, and

particularly as hydraulic fluids. However, in those applications whereit is important that the silicate ester be highly resistant todeterioration in the presence of water, those compounds should be chosenwherein at least one each of said R and R radicals in the structuralformula given above is a secondary, tertiary, or branched-chain primaryalkyl radical of from 3 to 16 carbon atoms, and more preferably, all theR and R radicals are of this character. As will be indicated in Table Igiven below, the silicon esters of the present invention whichincorporate such preferred groups have greatly superior hydrolyticstability charatceristics. It is also preferred that R be a straight orbranched-chain alkylene group of from 3 to 18 carbon atoms, at leastthree of which are in a chain between the adjacent oxygen atoms. Thefollowing compounds are representative of those which fall into thepreferred category: 1,3 -bis [tri- (2-butoxy) siioxy] propane 1,4-bis[tri (2butoxy) siloxy] butane 1,4-bis(di-tert.-butoxy-2-ethylbutoxysiloxy) butane Z-(dimethoxy tert.-butoxy siloxy)-5-(dipropoxy-2-butoxysiloxy) -hexane 1,4-bis[tri(2-butoxy)siloxyJpentane2,4-bis[tri(2-butoxy)siloxyJpentane 1,6-bis [tri 2-butoxy) siloxy]hexane 1,6-bis [di 2-butoxy) (tert.-butoxy) siloxy] hexane 1,4-bis[tri(2-ethyl-1-butoxy) siloxy] butane 2,4-bis [tri(2-ethyl-1-butoxy)siloxy]pentane 2,5 -bis [tri (Z-ethyl- 1 -butoxy) siloxy] hexane 1,5-bis tri Z-butoxy) siloxy] 2-methylpentane 2,4-bis [tri 2-butoxy siloxy]-2-methylpentane 1,l0-bis[tri(2-butoxy)siloxy]decane ll-tri(2-ethy1hexoxy) siloxy-7-tri- (terL-butoxy) -siloxy-4-isobutylheptane 1-(dipropoxy-2-butoxy siloxy) -4-(triisopropoxy siloxy)-pentane Still other compounds of this invention within the above generalformula can be described as the 1,2-bis- [tri(alkoxy)siloxy]alkanes andare of the type ha ving the general formula R1 R3 where the R s and theR s are saturated aliphatic radi cals of from 1 to 16 carbon atoms eachand'the R s, which may be the same or difierent, are hydrogen atoms oralkyl groups of from 1 to 4 carbon atoms each; The various R s mayrepresent the same or different radicals, and the same is true withrespect to the R radicals. Rep resentative R and R radicals are methyl,ethyl, isopropyl, sec.-butyl, tert.-buty1,' amyl, isoamyl, tert.-amyl,cyclopentyl, cyclohexyl, 2-ethylbutyl, 2-ethylhexyl, decyl, dodecyl, andthe like, while representative R radicals, in addition to the hydrogenatom, are methyl, ethyl, npropyl, isopropyl, n-butyl, sec.-butyl andtert.-butyl. Thus, exemplary compounds of this type coming within thescope of this invention are: l,2-bis[tri(ethoxy)siloxyJethane1-[tri(isopropoxy) siloxy] -2- [tri(2-butoxy -si1oxy] propane l-[dimethoxy) (ethoxy) siloxy] -2- [tri-isopropyoxy] ethane 2,3 -bis tri(Z-butoxy siloxy] pentane 2,3 -bis [tri(2-ethyll -butoxy siloxy]-4-tert.-butyl pentane 2,3-bis [tri (terL-butoxy) siloxy] butane 2,3-bis di tert.-bu toxy) (ethoxy) siloxy] butane 1- [tri(2-butoxy)siloxy]-2- [tri-(tert.-but0Xy)-Si10Xy] propane 1,2-bis [tri (tert.-butoxy)siloxy] ethane 1,2-bis [tri(tert.-amoxy) siloxy] ethane The silicateesters of the above type according to this invention also have a lowpour point and good viscosity and viscosity index properties, coupledwith low volatility even at high temperatures. Thus, the presentcompounds are adapted to be used at temperatures as low as 65 F., whiletheir viscosity at 210 F. is unusually good, i.e., from about 2.2 to 3.0cs. The ASTM slope of the viscosity-temperature curves of the presentcompounds is from about 0.65 to 0.70 as measured from 100 to 210 R,which relatively low slope values are indicative of correspondingly highviscosity-index qualities.

in view of the foregoing properties, and since the present compounds ofthe above type are also highly combustion resistant, it is obvious thatsaid compounds are useful as synthetic lubricants, and particularly ashydraulic fluids. However, in those applications where it is importantthat the silicate ester be highly resistant to deterioration in thepresence of water, those compounds should be chosen wherein at least oneeach of said R and R radicals in the structural formula given above is asecondary, tertiary, or branched-chain primary allcyl radical of from 3to 16 carbon atoms, preferably a tertiary alkyl radical of from 4 to 16carbon atoms, and more preferably, all the R and R radicals are of thischaracter. As will be indicated in Table I1 given below, the siliconesters of the present invention which incorporate such preferred groupshave greatly superior hydrolytic stability characteristics. Thefollowing compounds are representative of those which fall into thepreferred category:

1,2-bis [tri (tert.-butoxy) siloxy] ethane 1,2-bis [tri (tert.-arnoxy)siloxy] ethane 1,2-bis [tri( l-ethyll-methyl pentoxy) -siloxy]'ethane1,2-bis [di (tert.-butoxy) (2butoxy siloxy] ethane- 1- [tri(tert.-butoxysiloxy] -2 [di ethoxy) -tert.-hutoxy) siloxy] ethane 1-[tri(tert.-butoxy) siloxy]2- [tri (tert-amoxy siloxy] propane 1,2-bis[tri (tert.-butoxy) siloxy] propane 1,2-bis [tri (tert.-butoxy)siloxy]butane 2,3-bis [tri (tert.-butoxy) siloxy] butane 2,3-bis [tri(1,1,3-trimethylbutoxy) siloxy]pentane 1,2-bis [tri (tert.-butoxy)siloxy] pentane 1,2-bis [tri (tert.-butoxy) siloxy] hexane 3 ,4-bis [tri(tert.-butoxy) siloxy] hexane The ester compounds of this invention canreadily be prepared by the application of conventional methods oforganic syntheses. As a general rule, however, the first step is toreact the desired primary, secondary and/or tertiary alcohol withsilicon tetrachloride in the molar proportions required to form thetrialkoxymonochlorosilane. With primary and secondary alcohols thisreaction. readily takes place even at temperatures below F., while withtertiary alcohols, the recommended procedure is to add the alcohol alongwith pyridine to a cooled solution of SiCl in toluene (preferablymaintained below 0 F. to minimize loss of SiCL; by evaporation), withthe reaction then being completed by refluxing the mixture. When the Rand R groups are to be the same, the ester end product can then beformed by condensing the trialkoxymonochlorosilane with the desiredglycol (preferably in the presence of pyridine, ammonia or other acidacceptor). When the R groups are to be difierent from the R groups, apossible procedure is to first react onehalf of the hydroxy groups ofthe glycol with one of the trialkoxychlorosilane compounds, with theremaining portion of said hydroxy groups then being condensed with othertrialkoxychlorosilane derivative. However, since mixtures of esters ofthe type described herein are highly useful, the preferred practice whenemploying difierent trialkoxychlorosilane compounds is to react the samesimultaneously with the glycol. The mixture of di-(trialkoxysiloxy)alkanes (assuming an alkylene glycol reactant, for example) formed inthis manner can either be used as such, or it can be separated into twoor more of its component fractions, with each separated portion thenbeing used for hydraulic purposes or otherwise.

While, as indicated above, the silicon esters of this invention can beused alone for hydraulic fluid and other purposes, good results are alsoobtained with compositions wherein the present esters are blended with aminor percentage of other additive compounds. Thus, the oxidativestability of the present esters can be increased by the use of from 0.ito 10% by weight of an anti-oxidant, e.g., phenyl-a-naphthylamine,p-hydroxydiphenylamine, tertiary butylcatechol or the like. Improvedanti-wear, or extreme pressure, qualities can be imparted by theaddition of from 0.1 to 10% of a material of the type of tricresylphosphate, for example. Further, the viscosity characteristics of thepresent esters can be improved by the addition of from 0.1 to 10% of apolymeric viscosity index improver such as, for example, apolymethacrylate (Acryloid), a silicon such as dimethyl-, diethylormethyl phenyl silicone, or an alkoxypolysiloxane. The composition canalso be blended with minor amounts of other synthetic oils, such as thepoly-1,2-oxyalkylene glycols and the ether and/or ester derivativesthereof. Thus, use of from 1 to 20% of a polypropylene glycol (moleweight about 800) imparts improved stability characteristics tocompositions prepared from the present silicon esters and a conventionalviscosity index improver of the type note above. As rust inhibitors,there can be added from 0.1 to 10% of any one of several compounds,including metal sulfonates such as Zinc dipolypropene-benzene sulfonate,sodium white oil-benzene sulfonate, and the like. Particularlyattractive hydraulic fluids are those which incorporate a total of from70 to 98% by weight of the present silicon esters, together with 0.1 to10% each of a viscosity index improver, a rust inhibitor and(optionally) an antiwear agent.

The examples given below illustrate methods by which the compounds ofthe preferred type according to the present invention as described abovecan be prepared, Example I giving a typical preparation of atrialkoxymonochlorosilane intermediate.

EXAIVIPLE I Tri-(Z-Butoxy)Chlorosilane in this operation 1 mole of SiClwas charged to a flask and cooled to 15 C. To the "flask was then slowlyintroduced, with stirring, 3.2 moles of 2butanol, while maintaining thetemperature at 10 C. When the addition of the alcohol was complete, thetemperature was allowed to rise to about 20 C. and the agitationcontinued for three hours, with nitrogen being bubbled through themixture to carry off the HCl formed during the reaction. The crudeproduct was then distilled in vacuo, with the tri-(2-butoxy)chlorosilanebeing recovered in 78% yield as the fraction boiling at 7480 C. at 2.5mm. Hg.

EXAMPLE II 2 ,4-Bis [T ri (Z-Ethyl-I -Butoxy Si loxyJPentane In thisoperation, 0.184 mole 2-4-pentanediol, 0.51 mole pyridine and 225 ml.mixed xylenes were charged to a flask. To this solution 0.41 mole oftri(2-ethyl-1- butoxy) chlorosilane was added slowly with agitationwhile the temperature of the reaction mixture was maintained at -15 C.The resulting mixture was then heated to 100 C. for about one hour,cooled and filtered. The filter cake was twice reslurried with benzeneand filtered. The crude product was washed with water and distilled invacuo, the desired 2,4-bis [tri(Z-ethyl-l-butoxy) siloxy] pentaneproduct being recovered in yield as the fraction boiling at 241-245 C.at 1 mm. Hg.

EXAMPLE Ill 1,4-Bis[Tri(2-But0xy)Sil0xy]Butane In preparing the abovecompound, there were charged to a fiask 0.62 mole of tri(2-butoxy)chlorosilane and 75 ml. of mixed xylenes. To this mixture was slowlyadded 0.275 mole of 1,4-butanediol and 0.75 mole pyridine, the reactiontemperature being maintained at about 20 C. The mixture was thenrefluxed for two hours, after which the product was cooled, filtered,and the filter cake washed with xylene to separate any portion of thedesired product remaining in the solid pyridine hydrochloride. Thefiltrate and the xylene washings were then combined and distilled, withthe 1,4-bis [tri(2-butoxy)-siloxy] butane being recovered in 94% of thetheoretical yield as the fraction boiling at about 185-190 C. at 1 mm.Hg.

EXAMPLE 1V 1,4-Bis[Tri(2 Ethyl-l-Butoxy)SiloxyJButane This operation wasconducted using the same general method and conditions as described inExample 111 above, there being employed 0.41 mole oftri(2-ethyl-1-butoxy) chlorosilane, 0.184 mole of 1,4-butanedil, 0.51mole pyridine, and 225 ml. of mixed xylenes. The desired productcompound had a boiling point of 255-257 at 1 mm. Hg.

EXAMPLE V 1,4-Bis [Mixed Tri(2-Ethyl-1-Butoxy)Sil0xy and T ri(2-But0xy)S0l0xy]Butane In carrying out this operation, 0.2 mole of tri(2-butoxy)chlorosilane and 0.2 mole of tri(2-ethyl-lbutoxy)chlorosilane arecharged to a flask along with 180 ml. of mixed xylenes. To the flask wasthen slowly added a mixture of 0.184 mole of 1,4-butanediol, 0.51 moleof pyridine and 50 ml. of mixed xylenes, the temperature of the reactionmixture being held at about 23 C. during the addition period. Themixture was then refluxed for two hours, cooled and. filtered. Thefiltrate was then distilled, with the desired mixture of 1,4-bis[tri(2-ethyl 1 butoxy)siloxy]butane, 1,4-bis[tri(2-butoxy)siloxy]butanebeing recovered in 85% yield as the fraction boiling between about 185C. and 260 C. at 1 mm. Hg.

The data given in Table I which follows show the physical properties ofa number of different silicon esters coming within the scope of thepresent invention according to a preferred embodiment as illustrated bythe above examples. The items in the table are self-explanatory with theexception of the column marked Hydrolytic Stability. Hydrolyticstability was measured by contactthe compounds with refluxing distilledwater and observing for hazing or precipitation as evidence ofdecomposition. The time required for decomposition to become evident wastaken as the measure of hydrolytic stability and is so reported in thetable to follow.

In further illustration of still other compounds of the presentinvention and methods by which they are prepared, the followingadditional examples are given, Example VI being included as a typicalpreparation of a tri-(tert.-alkoxy)monochlorosilane.

EXAMPLE VI T ri-( Tert.-Butoxy) Ch lorosilane In this operation 340grams of silicon tetrachloride Was placed in a flask, and to this liquidwas then slowly added, over a two-hour period, a mixture of 450 grams oftert.-butanol, 720 grams of pyridine and 300 ml. of mixed xylenes, thereaction mixture being maintained at a temperature of about 0 C. duringthis period. The contents of the flask were then heated to 100 C. for 4hours, after which the mixture was combined with 500 ml. benzene,filtered, and stripped of its low boiling components under reducedpressure (50 mm. Hg). The residue was now fractionated, and 190 grams ofthe desired tri-(tert.-butoxy)chlorosilane product was: recovered as theportion boiling at about 46.7 C. at 1 mm. Hg.

EXAMPLE V11 1,2-Bis[Tri-(TerL-Butoxy)Siloxy]Etlzane To a mixture of 75grams of tri-(tert.-butoxy)chlorosilane and 40 ml. of xylene was addeddropwise a mixture of 7 grams of ethylene glycol and grams of pyridine.During this addition period the temperature rose to 62 C. The mixturewas now heated at 100 C. for 4.5 hours, after which it was cooled,filtered, and distilled in vacuo to yield grams of the desired1,2-bis[tri- (tert.-butoxy)siloxy]ethane product as the portion boilingat 148.9 C. at 1 mm. Hg. This product had a refractive index (u /D) of1.4074, a density (D 20/4) of 0.9361, and a viscosity at 100 and 210 F.of 19.7 es. and 3.96 cs., respectively.

EXAMPLE VIII 1,2-Bis[Tri- (2-But0xy)Sil0xy]Ethane In this operation, 300grams of tri-(2-butoxy)chlorosilane and 100 grams of xylene were placedin a flask, and to the contents of the flask was slowly added a mixtureof 30 grams of ethylene glycol and 100 grams of pyridine. The resultingmixture was then. refluxed for 3 hours, after which it was cooled,filtered. and distilled in vacuo. The desired1,2-bis[tri-(2-butoxy)siloxy]ethane product was recovered in 50% yieldas the portion boiling at 147-148 C. at 1 mm. Hg. It had a density (D20/4) of 0.9523, a refractive index (n /D) of 1.4172, viscosities at 65F., 100 F. and 210 F. of 480 cs., 6.5 es. and 2.37 cs., and an ASTMslope (65 to 210 F.) of 0.65.

TABLE I.-SUMMARY OF PHYSICAL PROPERTIES Boiling Refrae-VtscosityCentistokes at F. ASTM Slope t., 0., Density tive HydrolytlcCompound at 1 mm. 20/4 Index Stability Hg n /D -65 100 210 -65 to 100 to(Hrs) 1 t-Bis[tri(Q-butorw)-siloxylbutane 188 0. 9340 1. 4184 407 1275.92 2. 18 0. 06 0. 67 168 2I4-Bisltri(2-butoxy)-siloxy]pentane 174 0.9285 1. 4193 1, 701 7. 94 2. 56 0. 69 62} 1,4-Bis[tri(n-butoxy)-siloxy]butane 180 n 0, 0 1,3-Bisltri(2-butoxyl)silolxylriropane 0. 9449 34: 2. 22 0.68 04? 1 S-Bis'tritn-pro oxy st 0.pentane. 2:4Bisitri(Zethyfi-Lbutoxfisiloxy]pentane 241 -245 0. 9223 1.4340 3, 680 5:2 11. 1 3. 0. 66 0. 62 l 482,5-Bis[tri(Z-ethyl-l-butoxy)siloxy]hexane 274 0. 9226 1. 4359 2, 790010 11.8 3. 06 0. 63 0. 61 1 240 1,6-15is[tri(2-butoxy) iloxylhexane 1970. 9305 1. 4208 613 184 6. 88 2. 44 0.66 0. 6a 168 1,5-Bis[tri(2-butoxy)t xyl-2-methylpentane 182 0. 0329 1. 4212 1. 506 392 9. 2. 0.65 0.65 1400 2,li5is[tri(2-butoxy) xyl-2-methylpentane 177 2.113 481 9. e5 2. 980. 67 0. 66 1,10-13is[trit2-butoxy)-siloxy]decane 227 0.9229 1.4258 1,530 382 9. 96 3. 24 0.63 0. 62 38 l,3-Bis[tri(2 buto.\y) -Sil0xy]benzeno203 0. 9749 1. 4431 1, 154 280 7. 54 2. 55 0. 68 0. 66 42 1,4-Bis{tri(2butoxy)-Slloxy]benzene 215 0. 9757 1. 4430 1, 377 310 8. 47 2. :23 0. 660. 154 1,3-Bis[tri(2-propoxy)-siloxy]benzene 156 0. 9857 1. 4338 320 964.63 1. l4 0. 72 120 1,4-Bis[tri(2-propoxy)-si1oxy]benzene 152 0. 98584329 5. 38 1. 96 0 10 66 1 With 1% phenyl-cz-naphthylamine antioxidant.

7 EXAMPLE IX 1,2-Bis[Tri-(2-Butoxy)Siloxy]Propane In carrying out thispreparation, 400 grams of tri(2- butoxy)chlorosilane and 100 grams ofxylene were placed in a flask, and to this mixture was slowly added 120grams of pyridine and 47 grams of 1,2-propylene glycol, the temperaturerising to 70 C. during the addition. The mixture was then refluxed for10 hours, cooled, filtered and distilled in vacuo, 122 grams of thedesired 1,2-bis[tri(2-butoxy)siloxy1propane product being recovered asthe portion boiling at 162 C. at 1 mm. Hg. This compound has a density(D 20/4) of 0.9380, a refractive index (m /D) of 1.4158, viscosities at65 F., 100 F. and 210 F. of 476 cs., 5.88 cs. and 2.22 es, and an ASTMslope (-65 to 210 F.) of 0.66.

EXAMPLE X 2,3-Bis[ Tri- (Z-Butoxy Siloxy Butane In this operation therewas followed the same general procedure as described in Example IXexcept that there was employed 2,3-butanediol instead of the propyleneglycol. The desired product (recovered in 44% yield) had a boiling pointof 162 C. at 1 mm. Hg, 2. density (D 20/4) of 0.9368, a refractive index(n /D) of 1.4180, viscosities at 65 F., 100 F. and 210 F. of 1897 cs.,9.61 es. and 2.84 cs., and an. ASTM slope (-65 to 210 F.) of 0.68.

In Table II below a comparison is made as regards the hydrolyticstability of various of the silicate esters of the above type comingwithin the scope of this invention. This determination was made, as inthe previous test described above, by contacting the compounds withrefluxing distilled water and observing for hazing or precipitation asevidence of decomposition. The time required for decomposition to becomeevident was taken as the measure of hydrolytic stability.

TABLE II.-HYDROLYTIC STABILITY Hydrolytic Compound Stability (Hours)1,2-Bisltri(Z-etbyl-l-butoxy) -siloxy]ethme 0. 5

This application is a continuation-in-part of Abbott and Boltapplication Serial No. 352,596, filed May 1, 1953, now abandoned.

We claim:

1. Silicon esters of the group consisting of 1,4-bis [tri (2-butoxy)siloxy] butane, 2,4-bis [tri (2-butoxy) siloxy] pentane,

1,6-bis [tri (Z-butoxy) siloxy] hexane,

1,4-bis [tri(2-butoxy) siloxy] benzene, and

1,3-bis [tri (Z-propoxy) siloxy] benzene.

. 1,4-bis [tri (Z-butoxy siloxy] butane.

. 2,4-bis[tri(2-butoxy)siloxy1pentane.

. 1,6-bis [tri(2-butoxy) siloxyjlhexane.

. 1,4-bis [tri (Z-butoxy) siloxy] benzene.

. 1,3-bis [tri (2-propoxy) siloxy] benzene.

References Cited in the file of this patent UNITED STATES PATENTS2,566,957 Pedlow et al Sept. 4, 1951 2,643,263 Morgan June 23, 1953FOREIGN PATENTS 943,188 Germany May 17, 1956 OTHER REFERENCES Volnov etal.: Jr. Gen. Chem. (U.S.S.R.), vol. 10 (1940), pp. 550-56.

1. SILICON ESTERS OF THE GROUP CONSISTING OF 1,4-BIS(TRI(2-BUTOXY)SILOXY)BUTANE, 2,4BIS(TRI(2-BUTOXY)SILOXY)PENTANE,1,6-BIS(TRI(2-BUTOXY)SILOXY)HEXANE, 1,4-BIS(TRI(2-BUTOXY)SILOXY)BENZENE,AND 1,3-BIS(TRI(2-PROPOXY)SILOXY)BENZENE.